The present invention relates to attachments and liquid supply apparatuses that are preferably used in liquid ejection apparatuses. The present invention also relates to liquid containers and liquid supply apparatuses, and, more particularly, to liquid containers and liquid supply apparatuses that replace liquid cartridges in a liquid ejection apparatus, such as an inkjet recording apparatus, and allow supply of a liquid, such as ink, from an external source.
For example, an inkjet recording apparatus (a liquid ejection apparatus) typically includes an inkjet recording head (a liquid ejecting portion) and a paper feeder mechanism. The recording head is formed in a carriage and thus moved in a direction defined by the width of a sheet of recording paper. The paper feeder mechanism moves the paper sheet in a direction perpendicular to the movement direction of the recording head and relative to the recording head. The paper sheet is thus subjected to recording through ejection of ink droplets from the recording head in accordance with printing data.
If the inkjet recording apparatus is used on business, the apparatus must tolerate relatively large work load. It is thus necessary to employ a corresponding large-capacity cartridge. To meet such need, an off-carriage type recording apparatus including small-capacity sub tanks and main tanks serving as cartridges is known. The sub tanks are installed in the carriage in which the recording head is provided. The main tanks are arranged in a mounting portion (a cartridge holder), which is formed at, for example, a side of the body of the recording apparatus. Ink is supplied from each of the main tanks to the associated one of the sub tanks through an ink tube. The ink is then sent from the sub tanks to the recording head.
Further, to perform printing on a large-sized sheet of paper, it is now required to provide a large-sized recording apparatus that has an increased scanning distance of a carriage. The recording apparatus includes an increased quantity of nozzles formed in a recording head, thus improving the throughput of the apparatus.
To further improve the throughput of the apparatus, it is desirable that ink be fed from main tanks to sub tanks formed in a carriage when necessary while printing is being performed. The ink is thus stably supplied to the recording head through the sub tanks.
In this apparatus, each of the main tanks is connected to the corresponding one of the sub tanks through an ink supply tube provided specifically for each of the ink types employed by the apparatus. However, since the scanning distance of the carriage is relatively great in this apparatus, the length of each ink supply tube is increased and thus pressure variation occurs in the ink supply tube. Further, since the recording head includes the increased number of the nozzles, as has been described, the apparatus consumes an increased amount of ink. This raises the dynamical pressure of the ink in each ink supply tube, which connects the associated main tank to the sub tank. The amount of the ink supplied to the sub tank thus may become insufficient.
To solve this problem, for example, an inkjet recording apparatus having an ink supply valve unit, which includes a movable valve, has been proposed (see, for example, Japanese Laid-Open Patent Publication No. 2004-142405). The ink supply valve unit selectively opens and closes the valve in order to connect or disconnect an ink supply chamber with respect to a pressure chamber. The ink supply valve unit receives the ink that is to be supplied from a cartridge to a liquid ejection head, thus eliminating pressure variation in an ink supply tube.
Alternatively, for example, a structure in which air pressure is applied to a main tank has been proposed (see, for example, Japanese Laid-Open Patent Publications Nos. 2001-212974, 2001-287380, and 2003-311997). In this structure, an ink flow from the main tank to a sub tank is forcibly produced by the air pressure. A sufficient amount of ink free from pressure variation is thus supplied to the sub tank.
FIG. 24 is a view schematically showing a typical inkjet recording apparatus in which air pressure is applied to a main tank. FIG. 25 shows the structure of a cartridge 18 serving as the main tank.
As shown in FIG. 24, a recording head 15, a sub tank 103, a pressurization pump 20, and a cartridge holder 17 are formed in a printer 301. The cartridge holder 17 accommodates a cartridge 18 filled with ink Ik.
As is shown in detail in FIG. 25, the cartridge 18 includes a casing 39, which is a sealed casing formed of hard resin, and an ink pack 42 formed of flexible material. The ink pack 42 is received in the casing 39. An air inlet port 46 and a liquid outlet port 44 are defined in an end of the casing 39. Pressurized air is introduced from an external source to the ink pack 42 through the air inlet port 46. The pressurized air thus pressurizes and sends the ink Ik from the ink pack 42 to the exterior through the liquid outlet port 44. When the cartridge 18 is accommodated in the cartridge holder 17 of the printer 301, the liquid outlet port 44 and the air inlet port 46 are connected to the sub tank 103 and the pressurization pump 20, respectively.
Since the conventional cartridge 18 is supposed to be accommodated in the cartridge holder 17 of the printer 301, the size of the cartridge 18 is restricted correspondingly. A large-sized cartridge is thus actually unusable. In other words, the cartridge holder that accommodates the cartridge is formed in a restricted space in the printer. The amount of the ink retained in the cartridge is thus typically small. Thus, the greater the work load of the printer becomes, the more often the cartridge must be replaced. This complicates operation of the printer and raises the running cost of the printer. Particularly, if the printer is a small-sized type or a thin type and the space for accommodating the cartridge holder is restricted, the amount of the ink retained in the cartridge becomes correspondingly small. In this case, the above-described problem is pronounced.
Therefore, if the capacity of the cartridge must be increased, an external tank may be employed as an option for supplying the ink the external tank to the printer.
However, there may be a case in which the external tank for feeding the ink Ik is not compatible with a pressurization supply system of the ink Ik through the pressurization pump 20 of the printer 301. In this case, the printer 301 may cause an error in operation.
As described in Japanese Laid-Open Patent Publication No. 2003-326732, for example, an ink supply system using an attachment has been proposed. The attachment is mounted on a cartridge holder in the same manner as a cartridge, when the work load of the printer is relatively great. The ink is supplied from an external large-capacity ink tank to a recording head through the attachment. More specifically, a hollow sub tank is defined in the attachment, which is mounted on the cartridge holder. With the attachment mounted on the cartridge holder, the ink is introduced out of the external tank to the sub tank of the attachment to a predetermined level through actuation of a pump associated with the attachment. The ink is then sent from a liquid outlet port defined in a lower portion of the attachment to a liquid inlet port defined in the recording head.
However, when mounting the attachment of Japanese Laid-Open Patent Publication No. 2003-326732 on the cartridge holder, the pump must be activated to depressurize the sub tank of the attachment to a negative level. The ink is thus sent from the external tank to the sub tank until the ink level in the sub tank reaches the predetermined level. This prolongs the time needed for accomplishing the procedure for mounting the attachment. Further, it is necessary to install the pump, which sends the ink from the external tank to the sub tank, in association with the attachment. The cost for providing the attachment thus increases. That is, the attachment of Japanese Laid-Open Patent Publication No. 2003-326732 complicates the procedure for mounting the attachment on the cartridge holder as a replacement of the cartridge and increases the cost. In this regard, the attachment is not necessarily easy to employ.